INFLUENCE OF DEPOSITION PARAMETERS ON THE TEXTURE OF CHEMICAL-VAPOR-DEPOSITED TUNGSTEN FILMS BY A WF6 H-2/AR GAS-SOURCE/

In order to investigate the relationship between the film texture and the deposition parameters including gas composition, temperatures, and substrate materials, polycrystalline tungsten films were prepared by reduction of tungsten hexafluoride with hydrogen. The experimental res ults show that the orientations of the textured films correlate closel y with WF6 concentrations in the gas mixture and deposition temperatur es. High WF6 concentrations enhance the formation of the <100> texture d films, while low WF6 concentrations facilitate the formation of the <111> textured films. The <111> texture, usually observed in tungsten films deposited at high temperatures (greater than or equal to 400 deg rees C) and high ratios of H-2 to WF6, can also form at low deposition temperatures (370 degrees C) when the WF6 concentration used is low e nough (0.6 vol %). The WF6 concentration for obtaining a <100> texture d film increases with increasing deposition temperatures. On the other hand. the concentrations of hydrogen gas have minimal influence on th e formation of the film textures. Therefore, in terms of gas compositi on, the WF6 concentration, riot the ratio of H-2 to WF6 is a compact f actor which directly dominates the texture of the films. The effect of substrate on the film texture was only found in the initial growth st age. The crystals formed at the beginning of the film growth were rand omly oriented. A. preferential orientation became pronounced with incr easing film thickness through the competitive crystal growth.